The spiral ramp agitator for washer is generally of such a structure that a central shaft is set up vertically on the washing axis of the washer, a circular base is formed in one piece at the lower part of the central shaft, and several spiral ramp vanes of identical shapes are formed in one piece protruded between the central shaft and the base.
According such spiral ramp agitator, the washing is effected in such a way that as the washing axis rotates forwards or backwards by means of the driving force of a driving motor, the agitator fixed to the washing axis rotates forwards or backwards, and the wash water and articles filled in the intub are meanwhile agitated upwards, downwards, inwards and outwards in the intub.
Thus, according to an agitator washer in which wash is carried out by an agitating action of the agitator, the washing power is determined by the structure of agitator, speed and frequency of rotation, and the rotation speed and frequency of the agitator are related directly to its structure. For this reason, the performance of such a washer depends largely on the structure of the agitator.
Therefore, the agitator must have a shape suitable for improving the washing power on the one hand, and a high mechanical strength enough not to be easily damaged by any impact of the wash articles at the time of washing and a structure by which the wash articles are not damaged and preferably which is manufactured easily, on the other hand.
Up to now, many attempts have been made to change the shapes and structures of the agitators in various forms for the purpose of satisfying the above mechanical requirement, but none of them has obtained a result sufficient to satisfy concurrently the matters, such as improvement of washing power, high mechanical strength, protection of the wash articles from damage, reduction of load, easiness of manufacture, etc.
The conventional agitators as described in the U.S. Pat. No. 3,464,239 and No. 3,726,114 have, for example, disadvantage in that since the spiral ramp vanes formed in one piece at regular intervals on the periphery of the central shaft are uniformly formed thinly on the whole from the top toward the bottom, they are weak in strength and unable to stand for a long time any impact applied at the time of washing. Furthermore, they have also problems that some of the vanes being set up perpendicularly on the circular base, a very large load is imposed on the vanes, and the wash articles are caught on thin edge lines of each vane and damaged or even torn in some worse cases. In addition, such agitators has a problem in that it is impossible to expect a high washing effect due to a structural defect in each part of the agitator including the vanes.
In addition to the above-mentioned patents, such agitators of this type as disclosed in the U.S. Pat. Nos. 1,897,239, 1,923,580, 2,042,578, 2,150,654, 3,117,434 and the German Pat. No. 824,333, etc. are also included in the category similar to agitators as described in the above-mentioned patents, and they have also similar problems and defects. Moreover, some of them are so complex in structure that they lack a practicability.